1. Field of the Invention
The present invention is related to the fields of molecular biology, virology, immunology and medicine. The invention provides a composition comprising a virus-like particle (VLP) of an RNA-bacteriophage and at least one antigen, wherein the VLP is recombinantly produced in a host, and wherein the amount of host RNA with secondary structure comprised by the VLP is at most 20% of the amount of host RNA with secondary structure originally comprised by the VLP; and wherein the VLP and the at least one antigen are linked with one another.
The invention also provides methods for producing the compositions of the invention. The compositions of the invention are useful in the production of vaccines for the treatment of diseases, disorders and conditions. Furthermore, the compositions of the invention are particularly useful to efficiently induce strong antibody responses against the antigen within the indicated context while lowering or eliminating unwanted T cell responses.
2. Related Art
Virus-like particles (VLPs) of RNA-bacteriophages to which antigens are linked have been described to be useful vaccine compositions. Thus, WO 02/056905 describes VLP-antigen conjugates as vaccines for the treatment of infectious diseases, to prevent or cure cancer as well as to efficiently induce self-specific immune responses. Moreover, in the context of the induction of self-specific immune responses, specific VLP-antigen conjugates have been disclosed, for example, for the treatment of allergies (WO 03/040164) or bone diseases (WO 03/039225), or for the therapy and prophylaxis of conditions associated with the renin-activated angiotensin system (WO 03/031466).
Depending on the nature of the antigen and the related disease, certain types of immune response caused by the vaccine are usually more preferred over others. For example, while it is usually desirable to induce a strong cytotoxic T cell (CTL) response against tumor cells or viral infections, such a response, in particular for vaccines comprising self antigens, might result in serious adverse effect such as induction of self-specific T cells (Orgogozo, J. M. et al., Neurology 61, 46-54 (2003); Hock, C. et al., Natural Med. 8, 1270-75 (2002); Hock C. et al., Neuron 38, 547-554, (2003)).
Activation of antigen specific T cells largely depends on the cross-talk between T cells and the antigen presenting cells (APCs) such as dendritic cells, B cells and macrophages, which APCs present T cell antigens in the context of MHC molecules. One way leading to the activation of APCs is the interaction of CD40L on Th cells with CD40 on dendritic cells (Foy, T. M., et al., Annu. Rev. Immunol. 14:591 (1996)). Interestingly, this CD40L-mediated maturation of dendritic cells seems to be responsible for the helper effect on CTL responses. In fact, it has recently been shown that CD40-triggering by Th cells renders dendritic cells able to initiate a CTL-response (Ridge, J. P., et al., Nature 393:474 (1998); Bennett, S. R. M., et al., Nature 393:478 (1998); Schoenenberger, S. P., et al., Nature 393:480 (1998)).
Another way leading to the activation of APCs is through the activation of toll-like receptors expressed by APCs. So far ten human toll-like receptors have been identified, whose ligands exhibit a limited number of invariant patterns associated with pathogens (Medzhitov, R. and Janeway, C. A., Jr., Cell 91:295-298 (1997)). Examples of such patterns include lipopolysaccharides (LPS), non-methylated CG-rich DNA (CpG) or double stranded RNA, which are specific for bacterial and viral infections, respectively.
Generalized activation of APCs by factors that stimulate innate immunity may often be the cause for triggering self-specific lymphocytes and autoimmunity. Activation may result in enhanced expression of co-stimulatory molecules or cytokines such as IL-12 or IFNα. This view is compatible with the observation that administration of LPS together with thyroid extracts is able to overcome tolerance and trigger autoimmune thyroiditis (Weigle, W. O., Adv. Immunol. 30:159 (1980)). Moreover, in a transgenic mouse model, it was recently shown that administration of self-peptide alone failed to cause auto-immunity unless APCs were activated by a separate pathway (Garza, K. M., et al., J. Exp. Med. 191:2021 (2000)). The link between innate immunity and autoimmune disease is further underscored by the observation that LPS, viral infections or generalized activation of APCs delay or prevent the establishment of peripheral tolerance (Vella, A. T., et al., Immunity 2:261 (1995); Ehl, S., et al., J. Exp. Med. 187:763 (1998); Maxwell, J. R., et al., J. Immunol. 162:2024 (1999)). In this way, innate immunity not only enhances the activation of self-specific lymphocytes but also inhibits their subsequent elimination.
The virus-like particles of RNA phages, such as Qβ or AP205 described in the prior art and used as antigen carrier for vaccination have been prepared by recombinant expression from E. coli. The resulting VLPs obtained by subsequent purification from E. coli lysate, however, still contain encapsulated E. coli components, mainly E. coli RNA as well as some E. coli proteins. Many bacterial components, in particular bacterial nucleic acids, and hereby in particular bacterial DNA and bacterial RNA, cause stimulation of T-cell responses through the activation of toll-like receptors. As indicated, the activation of T cell responses might result in serious adverse effects. Moreover, the presence of substances such as unidentified bacterial components beside the proven pharmaceutically active ingredients within vaccines is undesired due to potential risks or side effects caused by such unidentified bacterial components.
Thus, there remains a need in the art for the development of new and potent vaccines for treating broader spectrum of diseases. In particular there remains a need in the art for the development of new vaccines, for which, to the great extent possible, unwanted side effects such as activation or stimulation of undesired T-cell responses are lowered or eliminated while a maximal therapeutical effect is maintained.